If you're going to be driving on holiday, I suggest you get the relevant international driving permit(s) for the country/countries you'll be driving in - there are 3, and they're not valid in the same places.
Get good travel insurance, including good medical cover, since for some of your trip you may not be able to use your EHIC and without medical cover would have to pay any emergency medical costs yourself.
Check everyone's passports have more than 6 months left before they expire. This is probably less of an issue in your particular case since you'll still be an EU citizen when you enter the EU, but it's advice the FCO has been emphasising recently, so prob worth doing anyway.
Don't panic about the actual travelling. It will probably take longer at airports and ports/Eurostar, so allow extra time, but you won't be stranded on holiday. The EU has passed contingency measures allowing travel to/from the UK to continue and you'll be going back to the UK, so there should be much less trouble if any - there's no risk of them saying you can't come in, if you have a British passport. (If you have an EU passport instead and just live in the UK, I'd ignore everything I just said and check with your country's embassy/consulate for advice...)
I don't think it's a stupid question to have asked at all. There's a lot of uncertainty around and talking to other people instead of searching on Google can be reassuring. (Obviously some people are less helpful than others, but don't let them get you down.) No one really knows what's going to happen over the next few weeks, but I'm sure everyone working on this in the background all acros the EU and the UK is doing their absolute best to put in place arrangements to make any changes that may be needed as smooth as possible. I hope you have a great, entirely trouble-free trip!